How to use the letsencrypt.constants function in letsencrypt

def create_le_config(parent_dir):
    """Sets up LE dirs in parent_dir and returns the config dict"""
    config = copy.deepcopy(constants.CLI_DEFAULTS)

    le_dir = os.path.join(parent_dir, "letsencrypt")
    config["config_dir"] = os.path.join(le_dir, "config")
    config["work_dir"] = os.path.join(le_dir, "work")
    config["logs_dir"] = os.path.join(le_dir, "logs_dir")
    os.makedirs(config["config_dir"])
    os.mkdir(config["work_dir"])
    os.mkdir(config["logs_dir"])

    return argparse.Namespace(**config)  # pylint: disable=star-args

def create_le_config(parent_dir):
    """Sets up LE dirs in parent_dir and returns the config dict"""
    config = copy.deepcopy(constants.CLI_DEFAULTS)
    config["strict_permissions"] = False

    le_dir = os.path.join(parent_dir, "letsencrypt")
    config["config_dir"] = os.path.join(le_dir, "config")
    config["work_dir"] = os.path.join(le_dir, "work")
    config["logs_dir"] = os.path.join(le_dir, "logs_dir")
    os.makedirs(config["config_dir"])
    os.mkdir(config["work_dir"])
    os.mkdir(config["logs_dir"])

    return argparse.Namespace(**config)  # pylint: disable=star-args

def config_with_defaults(config=None):
    """Merge supplied config, if provided, on top of builtin defaults."""
    defaults_copy = configobj.ConfigObj(constants.RENEWER_DEFAULTS)
    defaults_copy.merge(config if config is not None else configobj.ConfigObj())
    return defaults_copy

def flag_default(name):
    """Default value for CLI flag."""
    return constants.CLI_DEFAULTS[name]

def renewal_configs_dir(self):  # pylint: disable=missing-docstring
        return os.path.join(
            self.namespace.config_dir, constants.RENEWAL_CONFIGS_DIR)

def csr_dir(self):  # pylint: disable=missing-docstring
        return os.path.join(self.namespace.config_dir, constants.CSR_DIR)

def main(cli_args=sys.argv[1:]):
    """Command line argument parsing and main script execution."""
    sys.excepthook = functools.partial(_handle_exception, args=None)

    # note: arg parser internally handles --help (and exits afterwards)
    plugins = plugins_disco.PluginsRegistry.find_all()
    parser, tweaked_cli_args = create_parser(plugins, cli_args)
    args = parser.parse_args(tweaked_cli_args)
    config = configuration.NamespaceConfig(args)
    zope.component.provideUtility(config)

    # Setup logging ASAP, otherwise "No handlers could be found for
    # logger ..." TODO: this should be done before plugins discovery
    for directory in config.config_dir, config.work_dir:
        le_util.make_or_verify_dir(
            directory, constants.CONFIG_DIRS_MODE, os.geteuid(),
            "--strict-permissions" in cli_args)
    # TODO: logs might contain sensitive data such as contents of the
    # private key! #525
    le_util.make_or_verify_dir(
        args.logs_dir, 0o700, os.geteuid(), "--strict-permissions" in cli_args)
    setup_logging(args, _cli_log_handler, logfile='letsencrypt.log')

    # do not log `args`, as it contains sensitive data (e.g. revoke --key)!
    logger.debug("Arguments: %r", cli_args)
    logger.debug("Discovered plugins: %r", plugins)

    sys.excepthook = functools.partial(_handle_exception, args=args)

    # Displayer
    if args.text_mode:
        displayer = display_util.FileDisplay(sys.stdout)

Get a new certificate for the specified domains using the specified
        authenticator and installer, and then create a new renewable lineage
        containing it.

        :param list domains: Domains to request.
        :param plugins: A PluginsFactory object.

        :returns: A new :class:`letsencrypt.storage.RenewableCert` instance
            referred to the enrolled cert lineage, False if the cert could not
            be obtained, or None if doing a successful dry run.

        """
        certr, chain, key, _ = self.obtain_certificate(domains)

        if (self.config.config_dir != constants.CLI_DEFAULTS["config_dir"] or
                self.config.work_dir != constants.CLI_DEFAULTS["work_dir"]):
            logger.warning(
                "Non-standard path(s), might not work with crontab installed "
                "by your operating system package manager")

        if self.config.dry_run:
            logger.info("Dry run: Skipping creating new lineage for %s",
                        domains[0])
            return None
        else:
            return storage.RenewableCert.new_lineage(
                domains[0], OpenSSL.crypto.dump_certificate(
                    OpenSSL.crypto.FILETYPE_PEM, certr.body.wrapped),
                key.pem, crypto_util.dump_pyopenssl_chain(chain),
                configuration.RenewerConfiguration(self.config.namespace))

Get a new certificate for the specified domains using the specified
        authenticator and installer, and then create a new renewable lineage
        containing it.

        :param list domains: Domains to request.
        :param plugins: A PluginsFactory object.

        :returns: A new :class:`letsencrypt.storage.RenewableCert` instance
            referred to the enrolled cert lineage, False if the cert could not
            be obtained, or None if doing a successful dry run.

        """
        certr, chain, key, _ = self.obtain_certificate(domains)

        if (self.config.config_dir != constants.CLI_DEFAULTS["config_dir"] or
                self.config.work_dir != constants.CLI_DEFAULTS["work_dir"]):
            logger.warning(
                "Non-standard path(s), might not work with crontab installed "
                "by your operating system package manager")

        if self.config.dry_run:
            logger.info("Dry run: Skipping creating new lineage for %s",
                        domains[0])
            return None
        else:
            return storage.RenewableCert.new_lineage(
                domains[0], OpenSSL.crypto.dump_certificate(
                    OpenSSL.crypto.FILETYPE_PEM, certr.body.wrapped),
                key.pem, crypto_util.dump_pyopenssl_chain(chain),
                configuration.RenewerConfiguration(self.config.namespace))

def renewer_config_file(self):  # pylint: disable=missing-docstring
        return os.path.join(
            self.namespace.config_dir, constants.RENEWER_CONFIG_FILENAME)